Horn radiator adapted to be fed by a coaxial line



April 10, 1951 H. J. RIBLET ET AL HORN RADIATOR ADAPTED TO BE FED BY A COAXIAL LINE Filed April 30. 1946 FIG.3

S TR R E 0 LG m mm E RB v m m w ms N m HA J ATTORNEY Patented Apr. 10, 1951 HORN RADIATOR ADAPTED TO BE FED BY A CQAXIAL LINE Henry J. Riblet, Cambridge, Mass, and Jack Steinberger, Chicago, Ill., assignors, by mesne assignments, to the United States of America as represented by the Secretary of War Application April 30, 1946, Serial No. 665,938

1 Claim. 1

This invention relates to devices for radiating waves of electromagnetic energy such as used in high frequency communication systems including radio object-locating systems. More particularly the invention is directed to a device for adapting the principles of a flared horn type radiating element directly to the termination of a coaxial conductor transmission line or the like.

A radiating element of the horn type has wide application and can be used to match a waveguide transmission line to free space and thus may be used to radiate waves of electromagnetic energy directly to free space. Another application is in feeding energy to, and illuminating, a reflector adapted to direct energy into free space in any desired beam pattern. Heretofore, a horn type radiating element has required a hollow pipe waveguide for feeding energy thereto. In the cases where the energy is transmitted from its source by a coaxial line, it has been necessary to have a coupling device from the coaxial line to a hollow pipe waveguide for feeding the horn. The present invention eliminates the need for a coupling device by terminatinga coaxial conductor type transmission line in a flared horn type section.

Accordingly, it is one of the objects of the present invention to provide a flared termination to a coaxial conductor line whereby energy may be radiated directly therefrom.

It is another object of the invention to provide a horn type termination to a coaxial transmission line and in which the inner conductor is disposed in such a manner that it is effective as a dipole section, the orientation of the dipole section determining the plane of polarization of the radiant energy.

For a better understanding of the invention together with other and further objects thereof, reference is had to the following description of the invention taken in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic longitudinal sectional view of a coaxial transmission line according to the invention;

Fig. 2 is a front perspective view of a horn type termination to a coaxial transmission line according to the invention; and

Figs. 3 and 4 are sectional views taken on the lines 3-3 and d-4 of Fig. 2, respectively.

Referring to Fig. 1 there is shown a coaxial conductor transmission line H] having a center conductor H and an outer concentric conductor l2. Coaxial line It may be connected or coupled in any desired or well known manner to a (c1. zso-sacs) source of electromagnetic energy (not shown). The free end of outer conductor I2 is flared outwardly as at IE- to form a circular mouth M which has a greater diameter than that of the outer conductor l2- with the plane of the mouth or aperture substantially perpendicular to the axis of coaxial line Iii. The inner conductor H which would normally extend beyond'the free end of outer conductor I2 is bent nearthe end thereof in such a manner that the end portion [5 lies substantially in or parallel to the aperture plane 14 of the flared portion l3 with the end 16 of inner conductor ll approaching close to the periphery of the aperture it. As shown, the end It preferably is slightly spaced from, although it may actually touch and be connected to the peripheral portion of flared portion l3 forming aperture IA. The bent end portion 15 of inner conductor H acts in cooperation with the outer conductor as a dipole radiating element. When the end portion I 5 is oriented vertically, vertical polarization may be obtained and similarly when oriented in a horizontal manner, horizontal polarization results.

The dimensions of the coaxial line it, and of the angle of flare and length of the flared portion 13 may be determined to suit considerations of impedance matching and beam directivity according to established waveguide horn standards. It has been found that th standing wave ratio is small, the gain is relatively good and the frequency response is broad with the flared horn termination of a coaxial transmission line as hereinbefore described.

Figs. 2, 3 and 4 show a slight modification of the aforesaid structure which has more practical aspects as an antenna. In these figures, flared horn 20 is constructed in a manner similar to that described with reference to Fig. l. The flared portion 2| may be made as a separate casting of electrically conductive material which may be connected at its throat portion 22 to a coaxial conductor transmission line. To facilitate connections with the transmission line a suitable connecting or coupling member 23 may be provided. In this embodiment, the flared horn portion 2! is bent so that the plane of its mouth or aperture 24 is substantially parallel to the axis of the coaxial transmission line or of the throat portion 22. The inner conductor 25 is curved to follow the contour of the axis of the flared horn portion 2! and then bent at right angles so that the bent end portion 2% lies substantially parallel to the aperture .plane as shown more clearly in Fig. 4. Thus, the structure is similar to that described with reference to Fig. 1. If desired, the horn 2|] may be weatherized by inserting a sealing member 21 of dielectric material such as sold'under the trade name Styraloy in the aperture region of the horn 2G, a suitable groove 28 being provided in member 29 for receiving the bent end portion 26 of the inner conductor 25.

One advantage of the horn structure as shown in Figs. 2, 3 and 4 is that it may be rotated about the axis of the coaxial transmission lin for radiating energy through 360 in azimuth.

While there has been described what is at present considered the preferred embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

What is claimed is:

A horn-shaped radiating element for high frequency electromagnetic energy adapted to be connected directly to a coaxial conductor transmission line, comprising a throat portion adapted to be connected to the outer conductor of the coaxial line, a portion flared outwardly from said throat portion and terminating in a substantially circular open mouth, the rate of flare of said flared portion being designed to match the impedance of the coaxial line to the radiation impedance, said flared portion being bent, the plane of said open mouth being parallel to the axis of said throat portion, an inner conductor located substantially centrally within said throat and flared portions, one end of said inner conductor being adapted to be connected to the central conductor of the coaxial line, the opposite end of said inner conductor being located in the center of said open mouth, an end portion connected at one end to said opposite end of said inner conductor and located substantially in the plane of said open mouth, said end portion being effective as a radiating element, the orientation of said end portion determining the plane of polarization of the radiated energy, and weatherproofing material located across said open mouth and being provided with a groove for said end portion.

HENRY J. RIBLET. JACK STEINBERGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,281,274 Dallenbach et al. Apr. 28, 1942 2,425,716 Barrow Aug. 19, 1947 

